Hydrofoil system for boats



Oct. 21, 1958 G, BAKER 2,856,879

HYDROFOIL SYSTEM FOR BOATS Filed Sept. 13, 1956 10 Sheets-Sheet l okwCords Q41, H g-6 TTORNEYM J. G. BAKER I HYDROFOIL SYSTEM FOR BOATS Oct.21, 1958 Filed Sept. 13, 1956 10 Sheets-Sheet 2 NVE; UTOQ okw Cor/8m@QQQ I i Oct. 21, 1958 BAKER 2,856,879

HYDROFOIL SYSTEM FOR BOATS I Filed Sept. 13, 1956 10 Sheets-Sheet 3 Oct.21, 1958 J. a. BAKER 2,85

. HYDROFOIL SYSTEM FOR BOATS Fild Sept. 13, 1956 1o Sheets-Sheet 4 Oct.21, 1958 v BAKER 2,856,879

HYDROFOIL SYSTEM FOR BOATS Filed Sept. 13, 1956 v 10 Sheets-Sheet 5%-vs-Tcav= Qdokw Cordon \QDQXLBV I cRTremsv/v Oct. 21, 1958 J. G. BAKERHYDROFOIL SYSTEM FOR BOATS l0 Sheets-Sheet 6 Filed Sept. 13, 1956 Oct.21, 1958 J. G. BAKER HYDROFOIL SYSTEM FOR BOATS 10 Sheets-Sheet 7 FiledSept. 13, 1956 cnw Gordon makgr Oct. 21, 1958 J. G. BAKER HYDROFOILSYSTEM FOR BOATS 10 Sheets-Sheet a Filed Sept. 13, 1956 @vdom an:

J. G.BAKER 'HYDROFOIL SYSTEM FOR BOATS l0 Sheets-Sheet 9 Filed Sept. 13,1956 Oct. 21, 1958 J. G. BQAKER HYDROFOIL SYSTEM FOR BOATS l0Sheets-Sheet 1O Filed Sept. 13, 1956 ig-sq.

United States Patent This invention relates to a system of: hydrofoilsattached to the hull of a boat and adapted upon forward motion of theboat produced by a horizontally directed thrust to raise the boat andmaintain the same above the water during continuance of the propellingthrust. In certain of its aspects, the invention is more particularlyconcerned with a system in which the boat is supported at the bow by twooverhanging hydrofoils and at the 1 stern by a single hydrofoil. v

One object is to provide a hydrofoil boat of the'above character inwhich the front hydrofoils are arranged in a novel manner such as tominimize the overall width of the hydrofoil boat.

A second object is to adapt the rear hydrofoil for steering andincidence angle adjustment by a mounting disposed wholly within the boathull.

A third object is to provide a novel mounting which permits theincidence angle of one of the hydrofoils to be adjusted by a force whichis relatively small over a wide range of the incidence adjustment.

A fourth object is to provide a system for adjusting the incidence angleof a hydrofoil automatically to compensate for changes in the externallyapplied thrusts which tend to disturb the trim of the boat hull.

A fifth object is to balance the externally applied thrust forcesagainst a spring and utilize the displacement of the latter to effectthe incidence angle adjustment.

A sixth object is to provide an incidence angle adjusting system whichis adaptable forv practical use on sailboats.

A seventh object is to provide a hydrofoil sailboat in which the riggingis arranged in a novel manner such as to minimize the number of thrustforces required vto be combined in effecting the automatic incidenceadjustment of the incidence angle.

An eighth object is to effect the incidence angle adjustment in responseto changes in the tension of the rigging of the boat sail. i

The invention also resides in the novel manner of weighing and combininga plurality of different thrust forces and utilizing their resultant toeffect the incidence angle adjustment.

Other objects and advantages of the invention will become apparent fromthe following detailed description taken in connection with theaccompanying drawings, in which Figure-l is a perspective view of asailboat in operation with a hydrofoil system embodying the novelfeatures of the present invention.

Fig. 2 is a fragmentary side elevational view.

Fig. 3 is a fragmentary rear, end view.

Fig. 4 is a fragmentary section taken along the line 44 of Fig. 3.

Fig. 5 is a fragmentary perspective view of the mechanism shown in Fig.4. I

Fig. 6 is an enlarged fragmentary side view of a boat "ice stern withone of the rear hydrofoils broken and shown in section along the waterplane of the boat. I

Fig. 7 is a perspective view of the rear hydrofoil mounting bracket.

Fig. 8 is a fragmentary longitudinal section through the bow of thesailboat.

Fig. 9 is a fragmentary perspective view of a part of the incidenceangle adjusting mechanism.

Fig. 10 is a fragmentary sectional view of the incidence adjustingmechanism taken along the center line of the boat.

Fig. 11 is a fragmentary perspective view of part of the incidenceadjusting mechanism.

Fig. 12 is a fragmentary section taken along the line 12-12 of Fig. 10.

Fig. 13 is a schematic view of the incidence'angle ad- 1 justingmechanism.

Fig. 14 is a fragmentary schematic View illustrating the manner ofincorporating the incidence adjustment in:

a boat driven by an air propeller.

For purposes of illustration, the invention in its various aspects isshown in Figs. 1 to 13 of the drawings incorporated in a sailboat havingan elongated hull 10 adapted to float on the water but also adapted tobe sup ported above and out of contact with the water by a hydrofoilsystem comprising two front hydrofoils 11 overhanging opposite sides ofthe hull and a rear hydrofoil is described below.

board as used onconventional sailboats is necessary.

12 straddling the longitudinal center line of the boat at the stern andadjustable about an upright axis 13 10 steer the boat.

The main sail 15 isattached in the usual way to a mast 16 braced by afore, back and side stays 17,18 and 19 and carrying a boom 26 whoseangle is controlled by a sheet 21 extending around pulleys 22 movablealong a traveler 23. The usual jib 24 attached to the forestay 17 isadjusted by the jib sheet 25 extending around a sheave 26 attached tothe deck 27 close to the lower end of the mast. The latter is supportedon the deck through a ball joint 28 for universal swiveling of the mastabout a multiplicity of axes including a transverse axis 29 disposedinthe plane determined by the lines 30 to be Moreover, this arrangementpermits location of the hydrofoils closer to the sides of the boat thanwould be possible with V-shaped front hydrofoils for. example. Theoverall width of the boat is thus reduced to a minimum for a given topspeed and wind velocity.

In addition and for a purpose to appear later, the foils.

11 are located so as to dispose the lines 30 of action of their forcesin an upright plane which includes an axis 29 extending transversely ofthe center of the ball joint 28. To these several ends, the foils 11 aremounted on horizontal tubular bars 33 detachably coupled throughsuitable connections 3.3 with the outward ends of a tube 33* extendingtransversely through the hull below the deck 27 and projecting a shortdistance (Fig. 3) beyondopw po'site sides of the hull. The side stays 19may be anchored on the outer ends of the tube 33'.

To provide adequate lifting forces with foil elements of small chord forefficient high speed operation, each of the foils 11 is of the laddertype comprising a plurality of vertically spaced parallel liftingelements in the form of straight bars 34 spanning inner and outerstreamlined struts 35 to which the ends of the lifting elements arewelded. The elements 34 are of well known foil cross section (Fig. 6)and inclined upwardly and outwardly at angles such as to derive forcesdirected along the line 30 when the elements disposed at a properincidence angle are advanced edgewise through the water.

It will be observed that each of the ladder elements 34 exerts aseparate lifting force so that the total lifting force exerted at anytime increases with the degree of submergence of the elements. When theboat is floating on the water, the water surface rises to the line 37(Fig. 3). When the hull is foil borne (Fig. 1), that is, sustained abovethe water by the hydrofoils, the water surface intersects the foilelements along the line 38 (Fig. 3).

The rear hydrofoil 12 is constructed to serve as a rudder for steeringthe boat while the latter is floating on the water. To this end, itpreferably is of the ladder type comprising two elements 46) of V-shapevertically spaced from each other and rigidly joined at their ends tosubstantially parallel struts 41 of streamlined cross section. Thelatter straddle the stern of the boat and are normally rigid with andsuspended from depending arms 42 of a rigid frame 43 which, inaccordance with one aspect of the present invention, is supported withinthe boat hull to turn about the upright steering axis 13 and also abouta horizontal axis 44 (Figs. 4 and 5) extending transversely of anddisposed near but above the bottom 45 of the hull and spaced ahead ofthe boat stern. Both foils 40 are disposed below the water line 37 whenthe boat is floating but only a portion of the lower foil 40 issubmerged below the water line 38 (Fig. 3) when the boat is foil borneat top speed.

At all points along the active portions of the hydrofoil elements 40,the cross section taken in any vertical plane p (Fig. 3) is of astandard shape best shown in Fig. 6. The chord line 47 of each sectionis disposed in a novel angular relation with respect to the pivot axis44 so that the resultant of the forces exerted by the water actionproduces very little moment about the axis 44 in order to minimize theeffort required to adjust the incidence angle a and therefore thelifting effect of the foil. All of the hydrodynamic forces on the foil12 produce a resultant force 50 (Fig. 6) which may be considered asintersecting approximately at the center 51 of the chord line 47. Byplacing the cross section centers all along the lengths of the foilelements 40 in a common plane 49; by properly inclining the foil sectionchord lines 47 relative to the plane 49; and by setting the entire foilunit 12 so that the plane 49 is at the proper angle with the vertical 48when the thrust on the boat is just adequate to maintain the foil bornespeed of the boat constant, the resultant hydrodynamic force 50 may bedisposed approximately in the plane 49. To this end, the plane 49 istilted backwardly from the vertical 48 through an angle b of about 4.75degrees at the constant speed above referred to. In this position, theplane 49 of the resultant force 50 makes Referring now to Figs. 4 and5-, the frame 43 includes a horizontal tube disposed above and extendingtransversely across the stern portion of the boat and rigid at oppositeends with the arms 42 which project downwardly along opposite sides ofthe hull and are pivotally joined by pins 56 to the upper ends of thehydrofoil legs 41. Midway between its ends, the tube is welded orotherwise secured rigidly to the upper end of a shaft 57 extendingthrough and journaled in a tube 53 having alined tubular projections 59welded thereto near its lower end and paralleling the tube 55. Shortarms 60 depend rigidly from the outer ends of the projections 59 and arejoined by pivot pins 61 to ears 62 on a bracket 63 (Fig. 7) secured asby screws 64 to the bottom and side walls of the boat hull inside of thelatter. The pivot pins 61 are alined with each other.

As shown in Fig. 4, the shaft 57 is journaled in bearings 64* within thetube 58 and flanges 65 and 66 abut against opposite ends of the tubewhich thus sustains the weight on the rear hydrofoil 12. Rigid with thelower end of the shaft 57 are arms 67 projecting in opposite directionstransversely of the boat and yieldingly held in a straight frowardposition by springs 68' (Fig. 5) but. adapted to be swung back and forthto turn the frame 43 and the hydrofoil 12 about the upright axis 13 forsteering the boat to the right or left. For this purpose, the free endsof the arms 67 are connected to the ends of a crossed cable 63 extendingaround a drum 70 journaled on the hull and adapted to be rotated inopposite directions by a cable 71 movable back and forth by turning asteering wheel 72 located in a convenient position within the boat.

To provide for manual folding or lowering and raising of the rear orsteering hydrofoil 12 into and out of the water, the foil struts 41 areadapted to be turned about the pivots 56 as by turning a hand crank 72(Fig. 5) carried by the frame 43. This crank is on a shaft journaled ina housing 73 and carrying a worm 74 meshing with a Worm wheel 75 on ashaft 76 disposed alongside the tube 55 and carrying depending crankarms "77. The latter are coupled through adjustable links 78 withsimilar crank arms 79 fast on the pivot pins 56 and the legs 41 of thehydrofoil 12.

In accordance with a primary feature of the present invention, means isprovided for sensing and weighing the different and varying externalthrusts on the sail rigging tending to vary the pitch or trim of theboat and utilizing the resultant of such thrusts to automatically adjustthe angle of incidence of one or more of the hydrofoils to oppose andactually compensate for the effect of such thrust changes on the trim ofthe boat.

. It can be shown that this condition of proper trimming an includedangle 0 of about degrees with the rear end- I portion of the chord lines47. By locating the foil angle adjusting axis 44' and the foil steeringaxis 13 in the plane 49, the line of action of the resultanthydrodynamic force 50 on the foil unit 12 at any foil borne'constantspeed of the boat will substantially intersect both the incidence angleadjustment axis 44 and the steering axis 13. Thus the moment on the foil12 will be substantially zero at any speed.

Furthermore, under conditions of acceleration with this'arrangement, ithas beenfound that the moments on the foil about either the incidenceadjusting axis 4401' the steering axis 13 are either small or roughlyproportionalto the corresponding angular rotation of the foil unit so.that they can be roughly compensated for in the selection of thescale ofthe balancing spring to be describedlater. Thus either incidenceadjustment or steering can be carried out with little effort.

is achieved when the summation of all of the moments of the externallyapplied forces about the axis 29 is zero provided this axis isapproximately at the level of the center of gravity of the boat which isthe case in the present instance. Since the lines of action 31 of theresultant forces derived from the front hydrofoils, the forces due totensioning the jib sheet 25, and the load of the mast on the ball joint28 all intersect at the axis 29, these forces may be disregarded indetermining the. trimming moment about the axis 29. The remaining forcesto be considered in a sailboat are those exerted at the otherconnections between the sail rig and the boat hull. Of these forces, thecomponents which affect the trim of the hull at any time may bedetermined by the tension in the fore and back stays 17 and 18 and thelift exerted on the traveler 23.

The means for selecting and Weighing the values of these forcecomponents and computing the direction and the extent of the incidenceadjustment to compensate therefor includes in the present instance aframe 30 (Figs. 9 to 11) pivotally mounted within the boat hull andcoupled preferably mechanically with the back and forestays and thetraveler. The resultant of these force components thus applied to thecomputer frame are balance'd against the force of a spring 100 so thatthe resulting displacement of the frame is at all times a measure of thechange in the incidence angle of the rear hydrofoil which will offsetand compensate for the change in the trimming moment exerted on the boatby the sail rig and tending to detrim the same.

In the present instance the frame 80, is spaced a short distance fromthe operators position behind the steering wheel and comprises aplurality of tubes rigidly joined into a box-like truss structuresuspended to swing about an axis 81 extending transversely of the boathull. This axis is defined by studs 82 (Fig. 12) projecting inwardlyfrom bars 83 which are secured to plates 84 attached to the side Wallsof the hull. The studs 82 support bearings 85 on the ends of a tube 86joined by side tubes pending arm 103 on the computer frame. 'The link isurged rearwardly by a tension spring 122 anchored at 123 on the'bottomof the boat and stressed to exert on the frame 80 a substantially lesserforce than the spring 100 to maintain the computer linkage system undertension at all times.

The displacement of the computer frame 80 is transmitted to the mountingof the rear hydrofoil 12 to adjust the incidence angle a of this foiland thereby compensate for changes in the trimming moment due to changesin the. forces of the sail rig producing the displacement of 87 to across tube 88 having bearings 89 similarly journaled on the uprighttubes 90 of a generally H-shaped frame 91. The uprights 90 project upthrough openings 92 in the deck and are joined. at their upper ends bythe traveler 23 journaled at its ends on the frame '91. At their lowerends, the uprights are pivoted on the free ends of links 93 whoseopposite ends carry bearings 94 journaled on studs 95 projecting fromthe bars 83. The uprights 90 and the-traveler tube 23 are thus guidedfor upright movement and therefore adapted to select the propercomponent of the force applied to the traveler by the sheet 21. Thisforce component tends to swing the frame 80 clockwise as viewed in Fig.10.

I The counterbalancing spring 100 is stretched between a point 101 (Fig.2) of anchorage on the hull and a link ona bracket 102 adjustablysecured to an arm 103 depending from the bar 86 and forming part of theframe 80 by virtue of its rigid connection with the lower ends ofbracing tubes 104 converging downwardly from the bearings at the fourupper corners of the frame. Oscillation of the latter in service use isreduced by a hydraulic dampening device 105 (Fig. attached to a bracket-106 intermediate the ends of the depending arm 103.

The tension of the forestay representing one of the componentsdetermining the trimming moment exerted by the sail on the boat hull isapplied to the computer frame 80 through a cable 106 attached at 107 tothe frame and extending forwardly into the bow of the boat as shown inFig. 8 where it is connected to a rod 108 which is guided vertically soas to select the proper component of the forestay tension. For thispurpose, the lower end of the forestay is pivotally connected through asegment 109 to the end of the bar 108 which projects upwardly through ahole 110 in the deck. At its lower end, the bar 108 is pivoted on thefree end of a link 111 pivoted at 112 ona bracket 113 bolted to the bowof the hull.

At a point spaced above the link 111 the bar is pivotally joined to anarm 114 of a bell crank 115 which is pivoted on the bracket 113 at 116spaced behind the point 112 so that the arm 114 is somewhat longer thanthe link 111. A still longer arm 115 of the bell crank projectsdownwardly from the pivot 116 and is connected at its lower end to thecable 106. Thus the bar 108 is guided by the link 111 and 114 forupright movement which is applied to the computer frame 80 in agenerally horizontal direction as shown in Fig. 10. In this way thecomponent of the tension in the forestay which contributes to thetrimming moment on the hull is applied to the computer frame 80 in adirection to turn the latter counterclockwise as viewed in Fig. 10.

The tension in the backstay 18 which contributes to the trimming momenton the hull is applied to the computer frame 80 in a reverse direction.This is effected by extending the cable of the backstay around a pulley117 at the stern of the boat downwardly around a pulley 118 on the hullframe and then forwardly to a point 119 of connection to a link 120(Figs. 4 and 5). The latter extends along the bottom of the boat and isconnected at 121 (Figs. 10 and 11) to the extreme lower end of the dethetrimming moment due to the rear hydrofoil.

angular displacement of the frame 80 about its pivotal axis the computerframe. Such transmission is effected in the present instance simply byextending the link rear wardly as shown in Fig. 5 and connecting thesame at 124 to the lower end of a lever 125 fulcrumed at 126 on a block127 forming the nut of a screw 128. The latter is journaled in a boss129 on the frame casting 63 (Fig. 7). The upper short end of the lever125 ispivotally joined by a link 130 to lugs 131 formed on the tube 58near the upper end of the latter.

In the normally fixed position of. the fulcrum 126, it will be apparentthat a forward displacement of the link 120 by the computer Will tip thesupporting frame 43 0f the rear hydrofoil rearwardly about the axis 44and thereby correspondingly increase the incidence angle a of the foil.Conversely, this angle will be decreased in response to a clockwisedisplacement of the computer frame 80.

It will be apparent that the different forces contributing to thetrimming moment on the hu1l,'with the exception of that of the rearhydrofoil, are applied to the frame 80 and directed along linesindicated by the arrows in Fig. 13. The points 107, 121 and 23 ofapplication of these forces are located with respect to the pivotal axis81 of the frame 80 so that the forces act at moment arms r1, 12 and r3.These arms are of such length as to produce moments which arerespectively proportional to the corresponding moments acting on thehull.

It will be remembered from the description above that the force requiredto adjust the rear hydrofoil 12 about the axis 44 and thereby vary itsangle of incidence a is very small due to the location above describedof the plane 49 (Fig. 6). As a result of this and the ratio selected forthe lever 125, the force transmitted back to the computer frame 80through this lever and the link 120 is negligible in the moment itapplies to the frame 80 except for a small moment proportional to theangular movement of the hydrofoil 12 which is compensated for byproperly scaling the spring 100. It follows therefore that the resultantmoment on the frame 80 is proportional to the resultant trimming momenton the hull less The 81 is likewise proportional to the moment on thehull because of the linearload deflection characteristic of the spring100.

The scale of the spring 100 is chosen to properly relate the trimmingmoment of the forces acting on the hull and the angle of incidence ofthe foil and therefore the ultimate lifting force thereof.

Independent manual adjustment of the incidence angle may be effected byturning the screw 128 to thereby swing the lever 125 about its lower end124 as a fulcrum. For this purpose the screw shaft is coupled through auniversal joint 133 with a shaft 134 extended forwardly to the 0peratorsposition and adapted to be turned by a handcrank 135 (Fig. 2).

Fig. 14 shows another type of hydrofoil boat in which the incidenceangle adjusting mechanism may be used to advantage. In this boat,variations in the pitching moment exerted on the boat hull 10 resultfrom changes in the propelling thrust produced by a propeller supportedabove the hull and driven at different selected speeds by an engine 151.To facilitate sensing the thrust changes, the engine is mounted oncrossbars 152 through 7 at 155 on the bars and at their upper endspivotally joined to the engine casing. A parallelogram linkage is thusformed permitting fore and aft movement of the power unit.

The backwardly directed thrust exerted by the propeller is balancedagainst a contractile spring 157 anchored at 158 and connected to thelower end of a depending arm 15') forming an extension of the link 154.The engine and the drum are thus restrained against movement except inthe fore and aft direction in which the movement of the lever 154, 159is proportioned accurately in accordance with changes in the propellerthrust due to changes in the engine speed. Through a link 160, themotion of the arm is communicated to the lower end of the lever 125above described and thus utilized to adjust the incidence angle of therear hydrofoil l2 automatically. By correlating the ratios of theelements of the motion transmitting connections, the incidence angle maybe changed in direction and amount so as to produce a change in liftwhich just counterbalances each change in the pitching moment applied tothe boat hulL Vibration of the transmission linkage may be avoided byinterposing a suitable shock absorber 161 between the arm 159 and apoint 162 of anchorage on the boat hull.

I claim as my invention:

1. In a hydrofoil boat, the combination of, a hull, an upright tubewithin said hull having projections rigid with opposite sides of thetube and extending transversely of the hull, means rigid with said hulland supporting said projections for turning of said tube about ahorizontal axis disposed near the bottom of the hull, a shaft journaledin and extending through said tube, a crossbar rigid with the upper endof said shaft and extending substan tially horizontally and transverselyof the hull above the deck thereof, a hydrofoil unit having side legsrigidly suspended from the ends of said crossbar for adjustment withsaid crossbar and tube about said horizontal axis, and means connectedto said tube for rocking the same back and forth about said axis wherebyto adjust the ode:- tive angle of incidence of said hydrofoil unit.

2. in a hydrofoil boat, the combination of, a hull, an upright tubewithin said hull having projections rigid with opposite sides of thetube and extending transversely of the hull, means rigid with said hulland supporting said projections for turning of said tube about ahorizontal axis disposed adjacent the bottom of the hull, a shaftjournaled in and extending through said tube, a crossbar rigid with theupper end of said shaft and extending substantially horizontally andtransversely of the hull above the deck thereof, a hydrofoil unitrigidly suspended from said crossbar for adjustment with said crossbarand tube about said horizontal axis, means connected to said tube withinsaid hull for rocking the same back and forth about said axis whereby toadjust the effective incidence angle of said hydrofoil unit, and meanscoupled to the lower end of said shaft and operable to turn the shaftand said crossbar about the shaft axis and thereby steer the boatthrough the medium of said hydrofoil.

3. in a hydrofoil boat, the combination of, a hull, a crossbar disposedabove and extending across one'end of said hull, a hydrofoil havingupright side legs straddling said hull and rigidly joined to andsuspended from the overhanging ends of said crossbar, an upright supportwithin said hull rigid with said crossbar intermediate the ends thereof,a member journaled on said support to turn relative thereto about anupright axis, a frame disposed within and rigidly secured to said hull,means pivotally joining said frame and said member for swinging of thelatter about a horizontal axis extending transversely of said hull anddisposed Within the hull near the bottom thereof, and means operablefrom the interior of said hull for individually swinging said member andsaid support back and forth about said horizontal and upright axes.

4. In a hydrofoil boat, the combination of, a hull, a crossbar disposedabove and extending across one end of said hull, a hydrofoil havingupright side legs straddling said hull and rigidly joined to andsuspended from the overhanging ends of said crossbar, an upright supportwithin said hull rigid with said crossbar intermediate the ends thereof,a member journaled on said support to turn relative thereto about anupright axis, a frame disposed within and rigidly secured to said hull,means pivotally joining said frame and said member for swinging of thelatter about a horizontal axis extending transversely of said hull anddisposed within the hull near the bottom thereof, spring means acting onsaid member to urge the same to a straight ahead position, and meansoperable from the interior of said hull for individually swinging saidmember and said support back and forth about said horizontal and uprightaxes.

5. in a hydrofoil boat, the combination of, a hull, a crossbar disposedabove and extending across the stern of said hull, a hydrofoil havingupright side legs straddling said stern and rigidly joined to andsuspended from the overhanging ends of said crossbar, an upright supportwithin said hull joined to said crossbar intermediate the ends of thelatter, a frame disposed within and secured rigidly to said hull, meanspivotally joining said frame and support for swinging of the latterabout a horizontal axis extending transversely of said hull and disposedwithin the hull near the bottom thereof, and means for rocking saidsupport back and forth about said axis.

6. In a hydrofoil boat, the combination of, a hull, an upright tubewithin said hull having projections rigid with opposite sides of thetube and extending transversely of the hull, means rigid with said hulland supporting said projections for turning of said tube about ahorizontal axis disposed adjacent the bottom of the hull, a shaftjournaled in and extending through said tube, a cross bar rigid with theupper end of said shaft and extending parallel to said axis andtransversely of the hull above the deck thereof, arms rigid with anddepending from the outer ends of said crossbar beyond the sides of saidhull, a hydrofoil unit having upright side legs suspended from the lowerends of said arms and joined to the latter to swing about horizontalpivots alined with said axis, a second shaft journaled on said crossbarand having crank and link connections coupling the shaft rigidly to saidhydrofoil unit, and manually operable means for turning said secondshaft and thereby turn said hydrofoil unit about said axis.

7. A hydrofoil sailboat having, in combination, a hull, front and rearhydrofoils thereon for lifting and supporting the hull above the waterwhile in forward motion, a mast having a boom and mounted on said hullfor fore and aft swiveling, fore and back stays bracing said mast, meanson the bow and stern of said hull guiding the lower ends of said foreand back stays for upright movement relative to the hull, a travelercoupled to said boom by a sheet and mounted on said hull for uprightmovement, a computer element mounted in said bull to turn about a fixedaxis, means transmitting the load of said back stay and said traveler tosaid element to turn the same in one direction, a spring yieldablyrestraining said element against such turning, means transmitting themovement of said forestay to said element to turn the same in theopposite direction, and mechanism responsive to the resultant angulardisplacement of said element and operable to correspondingly adjust oneof said hydrofoils in a direction to change the angle of incidencethereof and compensate for the corresponding change in pitching momentapplied to said hull by the sail.

8. A hydrofoil sailboat having, in combination, a hull, front and rearhydrofoils thereon for lifting and supporting the hull above the waterwhile in forward motion, a mast, means on said hull mounting the lowerend of said mast for fore and aft swiveling of the mast, fore and backstays bracings said mast, means on the bow and stern of said hullguiding the lower ends of said fore and back stays, a computer elementmounted in said hull to turn about a fixed axis, means transmitting theloads of said back and forestays to said element tending to turn thelatter in opposite directions, a spring yieldably restraining saidelement against such turning, and mechanism responsive to the resultantangular displacement of said element and operable to correspondinglyadjust one of said hydrofoils in a direction to change the angle ofincidence thereof and compensate for each change in pitching momentapplied to said hull by the sail.

9. A hydrofoil sailboat having, in combination, a hull, front and rearhydrofoils thereon for lifting and supporting the hull above the waterwhile in forward motion, a mast, means on said hull mounting the lowerend of said mast for fore and aft swiveling of the mast, fore and backstays bracing said mast, means on the bow and stem of said hull guidingthe lower ends of said .fore and back stays for upright movementrelative to the hull, a computer element mounted in said hull to turnabout a fixed axis, means transmitting the loads of said backandforestays to said element tending toturn the latter in oppositedirections, a spring yieldably restraining said element against suchturning, and mechanism for communicating the resultant angulardisplacement of said element directly to said rear hydrofoil in adirection to adjust the angle of incidence and compensate for eachchange in pitching moment applied to said hull by the sail.

10. A hydrofoil sailboat having, in combination, a hull, front and rearhydrofoils thereon for lifting and supporting the hull above the waterwhile in forward motion, a mast, means coupling the lower end of saidmast to said hull for fore and aft swiveling of the mast, means forbracing said mast including a stay, means on said hull guiding the lowerend of said back stay foi upright movement relative to the hull, acomputer element mounted in said hull toturn about a fixed axis, meanstransmitting the loads of said stay to said element to turn the same inone direction, a spring yieldably restraining said element against suchturning, and mechanism for communicating the resultant angulardisplacement of said element'to said rear hydrofoil in a direction toadjust the angle of incidence and compensate for each change in pitchingmoment applied to said hull by the sail.

11. In a hydrofoil boat, the combination of, a hull, a hydrofoil systemmounted on said hull for lifting and supporting the same above thewaterwhile in forward motion including at least one hydrofoil having anangle of incidence adjustable to vary its lifting force and thereby trimthe hull, means for applying a thrust for propelling the hull forwardly,said thrust being variable in magnitude and directed horizontally alonga line spaced above the hull, and means responsive to changes in saidthrust and operable to adjust said incidence angle in a direction and byan amount to maintain the trim of the hull while the latter is foilborne.

12. In a hydrofoil boat, the combination of, a hull, fore and afthydrofoils for lifting and supporting said hull above the water while inforward motion, at least one hydrofoil having an angle of incidenceadjustableto vary the lifting force derived thereby, a member mounted onsaid hull for fore and aft movement, a spring yieldably restraining saidmovement of said member relative to said hull, means for applying ahorizontally directed thrust of variable magnitude to said member topropel thehull forwardly, and means for communicating the fore and aftmovements of said member to said adjustable hydrofoil to vary saidincidence angle in a direction and by an amount to maintain proper trimof the hull while the latter is foil borne.

13. In a hydrofoil boat, the combination of, a hull, fore and afthydrofoils for lifting and supporting said hull above the water while inforward motion, at least one hydrofoil having an angle ofincidence'adjust'able to the lifting force-derived thereby duringplaning, a member mounted on said hull for fore and aft movement, meansfor applying a propelling thrust of variable magnitude to said member,means yieldably biasing saidmember rearwardly relative to said hullwhereby the position of said member relative to said hull corresponds tothe magnitude of said propelling thrust, and means respon sive to thefore and aft movements of said member to correspondingly adjust saidadjustable hydrofoil and vary said incidence angle in a direction and byan amount to maintain proper trim of the hull while the latter is foilborne.

14. In a hydrofoil boat, the combination of, a hull, a plurality ofhydrofoils attached to said hull and adapted during forward motion ofthe hull to raise the same out of and maintain the hull above the watersurface, said hydrofoils being spaced apart longitudinally of said hulland at least one thereof having an adjustable angle of incidence, amember mounted on said hull and adapted to respond to the thrust forpropelling the boat forwardly, means for sensing changes in said thrust,and means responsive to said thrust changes and operable tocorrespondingly adjust said incidence angle and thereby change thelifting force to compensate for such changes whereby to maintain atrimmed position of said hull.

15. A hydrofoil sailboat having, in combination, a hull,

a sail rig including an upstanding mast, means intermediate the ends ofsaid hull supporting said mast to swivel about a horizontal axisextending transversely of the hull, three hydrofoils mounted on saidhull and operable to support said hull above the water when under wayand provide resistance for overcoming the side force and rolling momentof the sail, one of. said hydrofoils being mounted on said hull foradjustment about a transverse horizontal axis to vary its angleofincidence, and means responsive to changes in the trimming momentapplied by the sail rig to said hull and operable to adjust theincidence angle of said adjustable hydrofoil in a direction to overcomeand compensate for said trimming moment whereby to maintain the trim ofsaid hull in spite of changes in the magnitude of said trimming moment.

16. A hydrofoil sailboat having, in combination, a hull, a sailsupported thereon for exerting a propelling thrust directed along acenter of pressure spaced above the hull, and a pair of hydrofoilsattached to opposite sides of said hull and projecting below the bottomof said hull, said hydrofoils having lifting elements of foil crosssection converging downwardly toward the center plane of said hull andacting during forward motion of the hull through the water to exert onthe hull resultant lifting forces directed along lines which convergeupwardly and intersect said center plane at a point disposedsubstantially at the level of said center of pressure.

17. In a hydrofoil boat, the combination of, a hull, fore and afthydrofoils having active portions of foil cross section submergedin thewater for lifting and supporting said hull above the water in forwardmotion thereof, and means on said hull suspending one of said hydrofoilsfor swiveling about a horizontal axis extending transversely of the hulland spaced above the active portion of such hydrofoil, the cross sectionof said active portion having a chord line whose rear end portion makesan acute included angle of approximately degrees with an upright planeincluding said horizontal axis whereby the line of action of the liftingforce exerted by said hydrofoil lies substantially in said plane.

18. In a hydrofoil boat, the combination of, a hull, fore and afthydrofoils having active portions of foil cross section submerged in thewater for lifting and supporting said hull above the water while inforward motion, and means on said hull suspending one of said hydrofoilsfor swiveling about a horizontal axis extending transversely of the hulland spaced above the active portion of such 1 1 hydrofoil, the verticalcross sections of said active port'ionbeing spaced along the latter andextending longitudinally of the hull and having centers lying in asingle upright plane disposed at an acute included angle ofapproximately 85 degrees with the rear portion of the chord 5 of each ofsaid cross sections whereby the line of action of the lifting forceexerted by said hydrofoil is disposed close to said plane and the momentof such force about said axis is correspondingly reduced.

References Cited in the file of this patent UNITED STATES PATENTS

